Recently, small portable devices have become globally popular. At the same time, with the significant progress of high-speed information transmission networks, the demand for small, high-capacity nonvolatile memories have been rapidly expanding. Among them, in particular, NAND flash memories and small HDD (hard disk drive) have rapidly evolved in recording density and created a large market.
Under these circumstances, several ideas for novel memories have been proposed toward significantly exceeding the limit of memory density.
Among them, there is proposed a memory based on a resistance change material having a low resistance state and a high resistance state. More specifically, by applying a voltage pulse to the resistance change material, the low resistance state and the high resistance state can be repetitively changed. These two states are associated with binary data “0” and “1” to record data.
Known examples of such a resistance change material include ternary oxides containing transition metal elements such as perovskites and spinels (e.g., JP-2005-317787 (Kokai) and JP-A 2006-80259 (Kokai)) and binary oxides of transition metals (e.g., JP-A 2006-140464 (Kokai)). Furthermore, there is disclosed a technique using a solid solution formed by adding metals to various oxides (e.g., U.S. Patent Application Publication No. 2007/0269683A1).
It is pointed out that information recording/reproducing devices based on such resistance change materials have large power consumption, and low stability in repeated operation due to low thermal stability of each resistance state (e.g., S. Seo et al. Applied Physics Letters, vol. 85, p.p. 5655-5657).